This gap, known universally as the “doughnut hole,” is the most criticized and unpopular part of the Medicare prescription drug program.

However, the health care reform law of 2010 is gradually closing the coverage gap. From 2006, when Part D began, through 2010, falling into the gap meant having to pay 100 percent of your costs while in it. But now and in the future you will pay much less. It works like this:

Once your total drug costs (what your plan has paid plus your deductible and copays) exceed a certain amount ($2,850 in 2014) from the beginning of the calendar year, you are then in the gap.

While in the gap, in 2014 you pay 47.50 percent of the cost of brand-name drugs and 72 percent of generic drugs. (Fifty percent of the discount on brand-name drugs is paid by the companies that manufacture them, and the rest by the federal government. The discount on generic drugs is wholly paid by the federal government.) In subsequent years, these costs will reduce until, by 2020, you pay no more than 25 percent of the cost of any drug in the gap.

You get out of the gap when your out-of-pocket costs during the earlier part of the year (deductible and copays) plus anything you paid for drugs in the gap reach a certain dollar limit ($4,550 in 2014). The manufacturers’ contribution for brand-name drugs also counts toward this limit, even though you didn’t pay for it. But the government’s contribution for generic drugs does not count toward the limit.

If you reach this limit, catastrophic drug coverage kicks in automatically and your plan will pay 95 percent of your remaining costs until the end of the year.